1. Field of the Invention
This invention pertains generally to harvesting equipment, and more specifically to a rake tooth structure which has advantageous application to ground-driven rake wheels which are also referred to as horse rakes. Most specifically, the inventive rake tooth is used in combination with rake wheels having rims or hoops, which are commonly used to rake hay and other ground crops.
2. Description of the Related Art
In the handling of agricultural crop, it is common practice to cut the crop during a first pass through the field. During a subsequent pass, the crop will be raked into windrows. After the crop has had sufficient time to dry, then it is normally harvested.
With many agricultural crops, moisture content at the time of harvest is very consequential. Too much moisture will lead to the growth of various micro-organisms that can degrade or even poison the crop. Too little moisture often results in a lower quality product. Frequently then, there is a relatively narrow window of time within which the crop will be desirably harvested, and most desirably this moisture content will be as consistent throughout the crop as reasonably achievable. Once the crop has dried properly, then time is of the essence and the crop must be raked into a windrow efficiently, preparing for the harvesting machine.
In order to reduce the amount of labor and fuel needed to harvest a crop, and thereby improve the efficiency and lower the cost of production, machines have been developed and refined which vastly reduce the time required within a given field to accomplish the work. Regarding the raking of crop and the turning of windrows, various rakes have been devised through time that originally were pulled by animal and more recently by machine which will move and turn the crop with a minimum of direct human intervention. A large number of these machines are illustrated by Cornelis van der Lely and associates in U.S. Pat. Nos. 2,851,846; 2,874,529; 2,908,129; 2,908,130; 2,909,023; 2,909,024; 2,909,888; 2,926,481; 2,932,148; 3,057,145; 3,120,092; 3,127,727; 3,218,791; 3,447,295; 3,771,303; and 4,015,411; the contents of each which are incorporated herein by reference for their teachings of rakes. The majority of these rakes utilize rake wheels having a plurality of teeth upon each wheel. The wheels are pulled in a direction between their rotational and radial axes, which leads to interaction with the ground and subsequent rotation of the wheel. Any crop which contacts the teeth is swept to the side by the rotating rake wheel. With larger and more powerful machines, a plurality of rake wheels may be used to sequentially interact with the crop, to sweep it progressively farther to the side. A larger area may be raked in a single pass, thereby reducing the number of passes that must be made across the field, and consequently lowering the costs of fuel and labor. Nevertheless, the rake is somewhat limited in application, to crops and fields which do not excessively wear or damage the teeth.
While many crops or crop residues might desirably be raked by these rake wheels, equipment suitable for raking has heretofore only been available for crops such as alfalfa, hay or straw. In part this is due to the rake teeth, and the arrangement of wheels adjacent each other. For optimum raking efficiency, it is desirable to place the rake wheels closely adjacent each other. However, when an obstacle is encountered, a rake tooth may be deflected beyond elastic limits, and may then protrude from the rake wheel in a direction which interferes with an adjacent rake wheel. When this happens, the rake tooth will be further damaged or broken, and the adjacent rake wheel may also be damaged. As if that were not bad enough, the location of the broken tooth may not be immediately apparent, and may in fact not be discoverable. The tooth may remain in the windrow and may later be picked up by subsequent harvesting equipment. Steel is much harder than agricultural crop, and, should the steel rake tooth be picked up by the harvesting equipment, that equipment maybe seriously damaged.
In order to limit the amount of motion of a rake tooth out of the desired plane of rotation, van der Lely and others have devised various rims or hoops which encircle the rotary hub of the rake wheel. These rims help to maintain the correct spacing and position of each tooth, while still enabling the use of a large rake wheel. A large wheel is advantageous in the raking process to minimize the effects of uneveness in the field surface, enable adequate rotation of the ground-driven rake wheel, and enable significant movement of the crop perpendicular to the direction of travel of the towing tractor or similar agricultural vehicle. Progress has also been made in the hub structure itself, which enables replacement of rake teeth in many of the more modern designs.
While these rims which are concentric about the hub assist in maintaining tooth spacing, other problems have been identified by the present inventor. More particularly, in the prior art the teeth are effectively mechanically anchored at the rim, and undesirable stress is developed within the tooth in the region adjacent the rim. Consequently, when a rock, root or other hazard is encountered, all too often the stress induced in the tooth adjacent the rim is sufficient to exceed the elastic limit of the tooth, leading to the catastrophic failure described herein above, where the tooth will either immediately break or, worse, become entangled in an adjacent rake wheel.
Van der Lely and others were aware of this problem, but were unable to solve it. In fact, a number of the van der Lely patents referenced hereinabove are directed towards resolving this very issue. Changes to the tooth geometry, tooth length, method of attachment at the hub and at the ring, and other similar approaches have been proposed. Carr in U.S. Pat. No. 283,324; Pomeroy in U.S. Pat. No. 915,476; Martin, in U.S. Pat. No. 1,497,526; Bamford et al in U.S. Pat. No. 1,631,455; and Perold in U.S. Pat. No. 3,376,697; each incorporated herein by reference, illustrate various tooth geometries intended to reduce breakage or otherwise improve performance. Coils such as illustrated by Carr, Pomeroy and Bamford et al do not entirely eliminate the concentration of stress, and the coil tends to add significant, undesirable cost to the tooth and rake wheel. Sharp bends, regardless of location, even when adjacent the bolt such as illustrated by Martin, concentrate stresses within the tooth. Goodall et al in U.S. Pat. No. 2,867,965, also incorporated herein by reference, illustrates an alternative to the rims and hoops of the prior art. Johnston in U.S. Pat. Nos. 3,066,470 and 3,253,394; Luther et al in U.S. Pat. No. 3,226,922; Fishbaugh in U.S. Pat. Nos. 3,401,515 and 4,481,758; Miller in U.S. Pat. No. 3,481,125; Waser in U.S. Pat. No. 3,553,950; Fuller et al in U.S. Pat. No. 3,561,206; and Hein in U.S. Pat No. 4,473,994 all incorporated herein by reference, illustrated elastomeric connections between rims and teeth. The elastomeric material is intended to absorb stresses without exceeding the elastic limits of the rake teeth. While this approach does tend to reduce stress in the steel tooth, a tooth including the elastomeric material is far more expensive to manufacture, and is still prone to separation of the elastomer. Furthermore, aging sometimes leads to separation, independent of loads encountered in the field. Furthermore, the elastomeric material may actually allow the tooth to move out of the desired rotary path, and thereby adversely bind with adjacent rake wheels. In spite of the alterations proposed by these myriad patents on rake wheels, none has proven to be completely satisfactory. Consequently, rake teeth remain prone to undesirable breakage, leading to associated lost time spent in repair instead of raking. This slows the use of the rake in fields which present hazards that pose a thread to the rake teeth.
What is desired then is an improved rake wheel which overcomes the disadvantages of the prior art while not sacrificing the beneficial features of current rake wheels.
In a first manifestation, the invention is a rake tooth adapted for use in a ground-driven rake wheel having a rim concentric about a hub through which the rake tooth may pass. The rake tooth is configured to accommodate a variety of rim diameters and designs to allow ready repair and replacement of other diverse rake teeth. It has a first end attachable to a hub and a first leg extending therefrom. A working point forms the terminus of the first leg. A shank extends lengthwise from the first end towards the working point and has a general camber therein in a first direction of revolution forming an overall radius of curvature along its length. A working arc is between shank and working point, and has a general camber therein in a second direction of revolution forming an overall radius of curvature smaller than the overall radius of curvature of the shank.
In a second manifestation, the invention is a rake wheel for operative use in a ground-driven agricultural rake. The rake wheel has a central shaft, a hub rotationally mounted on the central shaft, a plurality of rake teeth attached to and extending from the hub and terminating in a plurality of working points, and a rim circumscribing the hub throught which rake teeth pass. A shank within each rake tooth extends lengthwise from the hub generally towards the working oint, and has a general camber in a first direction of revolution forming an overall radius of curvature. A working arc within each rake tooth extends between the shank and working point. The working arc has a general camber in the same direction of revolution as the shank, and forms an overall radius of curvature smaller than the overall radius of curvature of the shank.
A first object of the invention is to provide a rake tooth geometry which, through geometry alone, will resist breakage when a hazard is encountered. A second object of the present invention is the provision of a relatively simple geometry which is readily manufactured at low cost, most preferably at or lower than the cost of existing rake teeth. A third object of the invention is to accommodate existing rakes and rake wheels, and co-exist with adjacent rake wheels, whether outfitted with like rake teeth or not. Another object of the invention is to provide a rake tooth which is free of crop entanglement. A further object of the invention is the provision of a rake tooth which may be used with heavier, stronger, or more largely and deeply rooted forage crops. These and other objects are achieved in the preferred embodiment, which is explained in the following description and best understood when considered in conjunction with the appended drawing figures.